Simulation of solidification and cooling of a casting product using COMSOL Multiphysics

Sammanfattning: In this project, the cooling and solidification processes for a Valmet Foundry product have been simulated in order to shorten the cooling time. The study has also been done in cooperation with RISE Swecast in Jönköping, as a part of finding ways to make casting procedures more energy efficient. Another scope of the study is to evaluate how well COMSOL Multiphysics can be used to simulate these types of casting processes. A large part of the study has been about the simulation, but some information regarding material properties and process temperatures have been collected from RISE Swecast and Valmet. The model in COMSOL Multiphysics is based on a CAD file describing the casting product, and the surrounding sand form has been built around it as a part of the modeling. Initially, the current process was modeled and simulated to get the model to work as close to reality as possible. When the model describing the current case was deemed to be close enough to reality, some changes of the casting form were tested. The conductivity in the form was increased using metal fins, and a forced air stream was introduced to increase the convective heat flux of the sand form. The results of the studies shows that the cooling fins and air stream do not affect the cooling time notably by themselves, but combined they could make quite a big difference for the cooling process. The fins increase the turbulence of the introduced air flow which improves the convective heat transfer, and the cold air stream works as a heat sink for the fins. COMSOL Multiphysics is found to be an efficient way to model this type of procedures because of the way different physical concepts can be coupled, in this case heat transfer and turbulent air flow. It is also convenient to work with important CAD models in the program, and to model the phase change in a material. However, it demands a lot of knowledge about both the physics and how to build an effective mesh to get the most of the simulations.